Sirung volcano is located at the NE end of a 14-km-long line of volcanic centers that form a peninsula at the southern end of Pantar Island. The low, 862-m-high volcano is truncated by a 2-km-wide caldera whose floor often contains one or more small lakes. Much of the volcano is constructed of basaltic lava flows, and the Gunung Sirung lava dome forms the high point on the caldera's western rim. A number of phreatic eruptions have occurred from vents within the caldera during the 20th century. Forested Gunung Topaki, the 1390-m high point of the volcanic chain, lies at the SW end and contains a symmetrical summit crater.